This invention relates to a door frame and door assembly for a mine stopping, and more particularly to such an assembly for installation in a man-door opening in a mine stopping.
So-called "stoppings" are widely used in mines to stop off flow of air in passages in the mines, a stopping generally being a masonry (e.g., concrete block) or metal wall installed at the entrance of a passage to block flow of air therethrough. It is often desired that such stoppings be provided with a door, which is referred to as a "man door", for occasional access to the blocked-off passage. A serious problem is encountered, however, in providing a door for a stopping because heaving and shifting of the stopping such as often occurs may cause the door to become jammed, and may cause leakage of air contra to the purpose of the stopping.
The invention is in the same field as and may be regarded as representing an improvement upon the door for a mine stopping disclosed and claimed in our copending U.S. Pat. application Ser. No. 738,690, filed Nov. 4, 1976,